This research project is directed toward the total synthesis of some sesquiterpene lactones which have been shown to exhibit significant antitumor and/or anti-leukemic activity. Specific synthetic targets are elephantin and eupacunin, both of which are cyclodecadiene based natural products. Elephantin is being approached via intramolecular Diels-Alder cycloaddition of an allylic cyclobutadiene carboxylic ester and eventual cleavage of the (6.4.4.) fused ring system thus formed to a trans, trans-cyclodeca-1,5-diene. Eupacunin is being approached via direct formation of the requisite cis, cis-cyclodeca-1,6-diene followed by introduction of appropriate oxygen functionality.